1. Field of the Invention
The present invention relates to a key-entry type switch device (hereinafter referred to as a key switch device) subjected to a key-entry operation, and more particularly to a key switch device which may preferably be used for a keyboard incorporated as an input device in electronic equipment. The present invention also relates to a keyboard provided with a plurality of key switch devices.
2. Description of the Related Art
A thin or low-profile type keyboard has been incorporated in, for example, a notebook type personal computer or other electronic apparatuses. The keyboard is provided with a plurality of key switch devices for a key-entry operation. For example, a gear link-type key switch device is provided with a support plate, a key top arranged above the support plate, a pair of link members connected to the key top and interlocked with each other to guide a vertical or upward-and-downward motion of the key top above the support plate, and a membrane sheet switch capable opening and closing a contact section of an electrical circuit in accordance with the vertical motion of the key top. The link members are secured to the support plate by, for example, a frame-shaped housing. The support plate is attached at the front surface thereof to the back surface of the membrane sheet switch.
For example, Japanese Unexamined Patent Publication (Kokai) No. 2009-76321 (JP2009-76321A), Japanese Unexamined Utility Model Publication (Kokai) No. 5-66832 (JP5-66832U), and Japanese Unexamined Patent Publication (Kokai) No. 9-27235 (JP9-27235A) describe conventional key switch devices.
In the conventional key switch device, the support plate is formed from a metal material, such as a sheet metal or a stainless steel. Therefore, the support plate must have rigidity sufficient to prevent permanent deformation or breakage even when, for example, the support plate is subjected to a stress during the manufacturing or transporting process of a keyboard. Otherwise, a keyboard having a permanently deformed or broken support plate cannot be used as a finished product. Therefore, the support plate is required to have a certain extent of thickness for ensuring the rigidity. However, the thickness may impede reduction in weight and height of a key switch device.